Input sections `.ctors/.ctors.N` may go to either the output section `.init_array` or the output section `.ctors`:
* output `.ctors`: currently we sort them by name. This patch changes to sort by priority from high to low. If N in `.ctors.N` is in the form of %05u, there is no semantic difference. Actually GCC and Clang do use %05u. (In the test `ctors_dtors_priority.s` and Gold's test `gold/testsuite/script_test_14.s`, we can see %03u, but they are not really produced by compilers.)
* output `.init_array`: users can provide an input section description `SORT_BY_INIT_PRIORITY(.init_array.* .ctors.*)` to mix `.init_array.*` and `.ctors.*`. This can make .init_array.N and .ctors.(65535-N) interchangeable.
With this change, users can mix `.ctors.N` and `.init_array.N` in `.init_array` (PR44698 and PR48096) with linker scripts. As an example:
```
SECTIONS {
.init_array : {
*(SORT_BY_INIT_PRIORITY(.init_array.* .ctors.*))
*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors)
}
} INSERT AFTER .fini_array;
SECTIONS {
.fini_array : {
*(SORT_BY_INIT_PRIORITY(.fini_array.* .dtors.*))
*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors)
}
} INSERT BEFORE .init_array;
```
Reviewed By: psmith
Differential Revision: https://reviews.llvm.org/D91187
I noticed when running a large link with the --time-trace option that
there were several areas which were missing any specific time trace
categories (aside from the generic link/ExecuteLinker categories). This
patch adds new categories to fill most of the "gaps", or to provide more
detail than was previously provided.
Reviewed by: MaskRay, grimar, russell.gallop
Differential Revision: https://reviews.llvm.org/D90686
* For .cfi_*, GCC/GNU as emits SHT_PROGBITS type .eh_frame sections.
* Since rL252300, clang emits SHT_X86_64_UNWIND type .eh_frame sections
(originated from Solaris, documented in the x86-64 psABI).
* Some assembly use `.section .eh_frame,"a",@unwind` to generate
SHT_X86_64_UNWIND .eh_frame sections.
In a non-relocatable link, input .eh_frame are combined and there is
only one SyntheticSection .eh_frame in the output section, so the
"section type mismatch" diagnostic does not fire.
In a relocatable link, there is no SyntheticSection .eh_frame. .eh_frame of
mixed types can trigger the diagnostic. This patch fixes it by adding another
special case 0x70000001 (= SHT_X86_64_UNWIND) to canMergeToProgbits().
ld.lld -r gcc.o clang.o => error: section type mismatch for .eh_frame
There was a discussion "RFC: Usefulness of SHT_X86_64_UNWIND" on the x86-64-abi
mailing list. Folks are not wild about making the psABI value 0x70000001 into
gABI, but a few think defining 0x70000001 for .eh_frame may be a good idea for a
new architecture.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D85785
* If two group members are combined, we should leave just one index in the SHT_GROUP content.
* If a group member is discarded (/DISCARD/ or upcoming -r --gc-sections combination),
we should drop its index in the SHT_GROUP content. LLD currently crashes (`getOutputSection()` is null).
Reviewed By: psmith
Differential Revision: https://reviews.llvm.org/D84129
Essentially takes the lld/Common/Threads.h wrappers and moves them to
the llvm/Support/Paralle.h algorithm header.
The changes are:
- Remove policy parameter, since all clients use `par`.
- Rename the methods to `parallelSort` etc to match LLVM style, since
they are no longer C++17 pstl compatible.
- Move algorithms from llvm::parallel:: to llvm::, since they have
"parallel" in the name and are no longer overloads of the regular
algorithms.
- Add range overloads
- Use the sequential algorithm directly when 1 thread is requested
(skips task grouping)
- Fix the index type of parallelForEachN to size_t. Nobody in LLVM was
using any other parameter, and it made overload resolution hard for
for_each_n(par, 0, foo.size(), ...) because 0 is int, not size_t.
Remove Threads.h and update LLD for that.
This is a prerequisite for parallel public symbol processing in the PDB
library, which is in LLVM.
Reviewed By: MaskRay, aganea
Differential Revision: https://reviews.llvm.org/D79390
This is part of the Propeller framework to do post link code layout
optimizations. Please see the RFC here:
https://groups.google.com/forum/#!msg/llvm-dev/ef3mKzAdJ7U/1shV64BYBAAJ and the
detailed RFC doc here:
https://github.com/google/llvm-propeller/blob/plo-dev/Propeller_RFC.pdf
This patch adds lld support for basic block sections and performs relaxations
after the basic blocks have been reordered.
After the linker has reordered the basic block sections according to the
desired sequence, it runs a relaxation pass to optimize jump instructions.
Currently, the compiler emits the long form of all jump instructions. AMD64 ISA
supports variants of jump instructions with one byte offset or a four byte
offset. The compiler generates jump instructions with R_X86_64 32-bit PC
relative relocations. We would like to use a new relocation type for these jump
instructions as it makes it easy and accurate while relaxing these instructions.
The relaxation pass does two things:
First, it deletes all explicit fall-through direct jump instructions between
adjacent basic blocks. This is done by discarding the tail of the basic block
section.
Second, If there are consecutive jump instructions, it checks if the first
conditional jump can be inverted to convert the second into a fall through and
delete the second.
The jump instructions are relaxed by using jump instruction mods, something
like relocations. These are used to modify the opcode of the jump instruction.
Jump instruction mods contain three values, instruction offset, jump type and
size. While writing this jump instruction out to the final binary, the linker
uses the jump instruction mod to determine the opcode and the size of the
modified jump instruction. These mods are required because the input object
files are memory-mapped without write permissions and directly modifying the
object files requires copying these sections. Copying a large number of basic
block sections significantly bloats memory.
Differential Revision: https://reviews.llvm.org/D68065
Currently, `error: incompatible section flags for .rodata` is reported
when we mix SHF_LINK_ORDER and non-SHF_LINK_ORDER sections in an output section.
This is overconstrained. This patch allows mixed flags with the
requirement that SHF_LINK_ORDER sections must be contiguous. Mixing
flags is used by Linux aarch64 (https://github.com/ClangBuiltLinux/linux/issues/953)
.init.data : { ... KEEP(*(__patchable_function_entries)) ... }
When the integrated assembler is enabled, clang's -fpatchable-function-entry=N[,M]
implementation sets the SHF_LINK_ORDER flag (D72215) to fix a number of
garbage collection issues.
Strictly speaking, the ELF specification does not require contiguous
SHF_LINK_ORDER sections but for many current uses of SHF_LINK_ORDER like
.ARM.exidx/__patchable_function_entries there has been a requirement for
the sections to be contiguous on top of the requirements of the ELF
specification.
This patch also imposes one restriction: SHF_LINK_ORDER sections cannot
be separated by a symbol assignment or a BYTE command. Not allowing BYTE
is a natural extension that a non-SHF_LINK_ORDER cannot be a separator.
Symbol assignments can delimiter the contents of SHF_LINK_ORDER
sections. Allowing SHF_LINK_ORDER sections across symbol assignments
(especially __start_/__stop_) can make things hard to explain. The
restriction should not be a problem for practical use cases.
Reviewed By: psmith
Differential Revision: https://reviews.llvm.org/D77007
Add new method getFirstInputSection and use instead of getInputSections
where appropriate to avoid creation of an unneeded vector of input
sections.
Differential Revision: https://reviews.llvm.org/D73047
Currently LLD always use zlib compression level 6.
This patch changes it to use 1 for -O0, -O1 and 6 for -O2.
It fixes https://bugs.llvm.org/show_bug.cgi?id=44089.
There was also a thread in llvm-dev on this topic:
https://lists.llvm.org/pipermail/llvm-dev/2018-August/125020.html
Here is a table with results of building clang mentioned there:
```
Level Time Size
0 0m17.128s 2045081496 Z_NO_COMPRESSION
1 0m31.471s 922618584 Z_BEST_SPEED
2 0m32.659s 903642376
3 0m36.749s 890805856
4 0m41.532s 876697184
5 0m48.383s 862778576
6 1m3.176s 855251640 Z_DEFAULT_COMPRESSION
7 1m15.335s 853755920
8 2m0.561s 852497560
9 2m33.972s 852397408 Z_BEST_COMPRESSION
```
It shows that it is probably not reasonable to use values greater than 6.
Differential revision: https://reviews.llvm.org/D70658
sections, but the current code misses certain variants. In particular, those
named when clang takes the code path in
clang/lib/Driver/ToolChain.cpp:416, where crtfiles are named:
clang_rt.<component>-<arch>-<env>.<suffix>
Previously, the code only handled:
clang_rt.<component>.<suffix>
<component>.<suffix>
This revision fixes that.
This makes it clear `ELF/**/*.cpp` files define things in the `lld::elf`
namespace and simplifies `elf::foo` to `foo`.
Reviewed By: atanasyan, grimar, ruiu
Differential Revision: https://reviews.llvm.org/D68323
llvm-svn: 373885
Fixes PR38748
mergeSections() calls getOutputSectionName() to get output section
names. Two MergeInputSections may be merged even if they are made
different by SECTIONS commands.
This patch moves mergeSections() after processSectionCommands() and
addOrphanSections() to fix the issue. The new pass is renamed to
OutputSection::finalizeInputSections().
processSectionCommands() and addorphanSections() are changed to add
sections to InputSectionDescription::sectionBases.
finalizeInputSections() merges MergeInputSections and migrates
`sectionBases` to `sections`.
For the -r case, we drop an optimization that tries keeping sh_entsize
non-zero. This is for the simplicity of addOrphanSections(). The
updated merge-entsize2.s reflects the change.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D67504
llvm-svn: 372734
This patch is mechanically generated by clang-llvm-rename tool that I wrote
using Clang Refactoring Engine just for creating this patch. You can see the
source code of the tool at https://reviews.llvm.org/D64123. There's no manual
post-processing; you can generate the same patch by re-running the tool against
lld's code base.
Here is the main discussion thread to change the LLVM coding style:
https://lists.llvm.org/pipermail/llvm-dev/2019-February/130083.html
In the discussion thread, I proposed we use lld as a testbed for variable
naming scheme change, and this patch does that.
I chose to rename variables so that they are in camelCase, just because that
is a minimal change to make variables to start with a lowercase letter.
Note to downstream patch maintainers: if you are maintaining a downstream lld
repo, just rebasing ahead of this commit would cause massive merge conflicts
because this patch essentially changes every line in the lld subdirectory. But
there's a remedy.
clang-llvm-rename tool is a batch tool, so you can rename variables in your
downstream repo with the tool. Given that, here is how to rebase your repo to
a commit after the mass renaming:
1. rebase to the commit just before the mass variable renaming,
2. apply the tool to your downstream repo to mass-rename variables locally, and
3. rebase again to the head.
Most changes made by the tool should be identical for a downstream repo and
for the head, so at the step 3, almost all changes should be merged and
disappear. I'd expect that there would be some lines that you need to merge by
hand, but that shouldn't be too many.
Differential Revision: https://reviews.llvm.org/D64121
llvm-svn: 365595
We currently (ab)use the Live bit on output sections to track whether
the section has ever had an input section added to it, and then later
use it during orphan placement. This will conflict with one of my upcoming
partition-related changes that will assign all output sections to a partition
(thus marking them as live) so that they can be added to the correct segment
by the code that creates program headers.
Instead of using the Live bit for this purpose, create a new flag and
start using it to track the property explicitly.
Differential Revision: https://reviews.llvm.org/D62348
llvm-svn: 362444
This change causes us to read partition specifications from partition
specification sections and split output sections into partitions according
to their reachability from partition entry points.
This is only the first step towards a full implementation of partitions. Later
changes will add additional synthetic sections to each partition so that
they can be loaded independently.
Differential Revision: https://reviews.llvm.org/D60353
llvm-svn: 361925
Make some small adjustment while touching the code: make parameters
const, use less_first(), etc.
Differential Revision: https://reviews.llvm.org/D60989
llvm-svn: 358943
Recommit r356666 with fixes for buildbot failure, as well as handling for
--emit-relocs, which we decide not to emit any relocation sections as the
table is already position independent and an offline tool can deduce the
relocations.
Instead of creating extra Synthetic .ARM.exidx sections to account for
gaps in the table, create a single .ARM.exidx SyntheticSection that can
derive the contents of the gaps from a sorted list of the executable
InputSections. This has the benefit of moving the ARM specific code for
SyntheticSections in SHF_LINK_ORDER processing and the table merging code
into the ARM specific SyntheticSection. This also makes it easier to create
EXIDX_CANTUNWIND table entries for executable InputSections that don't
have an associated .ARM.exidx section.
Fixes pr40277
Differential Revision: https://reviews.llvm.org/D59216
llvm-svn: 357160
There is a reproducible buildbot failure (segfault) on the 2 stage
clang-cmake-armv8-lld bot. Reverting while I investigate.
Differential Revision: https://reviews.llvm.org/D59216
llvm-svn: 356684
Instead of creating extra Synthetic .ARM.exidx sections to account for
gaps in the table, create a single .ARM.exidx SyntheticSection that can
derive the contents of the gaps from a sorted list of the executable
InputSections. This has the benefit of moving the ARM specific code for
SyntheticSections in SHF_LINK_ORDER processing and the table merging code
into the ARM specific SyntheticSection. This also makes it easier to create
EXIDX_CANTUNWIND table entries for executable InputSections that don't
have an associated .ARM.exidx section.
Fixes pr40277
Differential Revision: https://reviews.llvm.org/D59216
llvm-svn: 356666
This lets us remove the special case from Writer::writeSections(), and also
fixes a bug where .eh_frame_hdr isn't necessarily written in the correct
order if a linker script moves .eh_frame and .eh_frame_hdr into the same
output section.
Differential Revision: https://reviews.llvm.org/D58795
llvm-svn: 355153
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Patch from Andrew Kelley.
For context, see https://bugs.llvm.org/show_bug.cgi?id=39862
The use case is embedded / OS programming where the kernel wants
access to its own debug info via mapped dwarf info. I have a proof of
concept of this working, using this linker script snippet:
.rodata : ALIGN(4K) {
*(.rodata)
__debug_info_start = .;
KEEP(*(.debug_info))
__debug_info_end = .;
__debug_abbrev_start = .;
KEEP(*(.debug_abbrev))
__debug_abbrev_end = .;
__debug_str_start = .;
KEEP(*(.debug_str))
__debug_str_end = .;
__debug_line_start = .;
KEEP(*(.debug_line))
__debug_line_end =
.;
__debug_ranges_start
= .;
KEEP(*(.debug_ranges))
__debug_ranges_end
= .;
}
Differential revision: https://reviews.llvm.org/D55276
llvm-svn: 348291
The uint32_t type does not clearly convey that these fields are interpreted
in the target endianness. Converting them to byte arrays should make this
more obvious and less error-prone.
Patch by James Clarke
Differential Revision: http://reviews.llvm.org/D54207
llvm-svn: 346893
Out::DebugInfo was used only by GdbIndex class to determine if
we need to create a .gdb_index section, but we can do the same
check without it.
Added a test that this patch doesn't change the existing behavior.
llvm-svn: 345058
Previously, if you invoke lld's `main` more than once in the same process,
the second invocation could fail or produce a wrong result due to a stale
pointer values of the previous run.
Differential Revision: https://reviews.llvm.org/D52506
llvm-svn: 343009
The current support for V1 ABI in LLD is incomplete.
This patch removes V1 ABI support and changes the default behavior to V2 ABI,
issuing an error when using the V1 ABI. It also updates the testcases to V2
and removes any V1 specific tests.
Differential Revision: https://reviews.llvm.org/D46316
llvm-svn: 331529
Currently LLD sets OutSecOff in addSection for input sections.
That is a fake offset (just a rude approximation to remember the order),
used for sorting SHF_LINK_ORDER sections
(see resolveShfLinkOrder, compareByFilePosition).
There are 2 problems with such approach:
1. We currently change and reuse Size field as a value assigned. Changing size is
not good because leads to bugs. Currently, SIZEOF(.bss) for empty .bss returns 2
because we add two empty synthetic sections and increase size twice by 1.
(See PR37011: https://bugs.llvm.org/show_bug.cgi?id=37011)
2. Such approach simply does not work when --symbol-ordering-file is involved,
because processing of the ordering file might break the initial section order.
This fixes PR37011.
Differential revision: https://reviews.llvm.org/D45368
llvm-svn: 329560
Our code assumes all input sections in an output SHF_LINK_ORDER
section has SHF_LINK_ORDER flag. We do not check that and that can cause a crash.
That happens because we call
std::stable_sort(Sections.begin(), Sections.end(), compareByFilePosition);,
where compareByFilePosition predicate does not expect to see
null when calls getLinkOrderDep.
The same might happen when sections refer to non-regular sections.
Test cases demonstrate the issues, patch fixes them.
Differential revision: https://reviews.llvm.org/D44193
llvm-svn: 327006
This should resolve the issue that lld build fails in some hosts
that uses case-insensitive file system.
Differential Revision: https://reviews.llvm.org/D43788
llvm-svn: 326339
This fixes pr36475.
I think this code can be simplified a bit, but I would like to check
in the more direct fix if we are in agreement on the direction and
then refactor.
This is not something that bfd does. The issue is not noticed in bfd
because it keeps fewer sections from the linkerscript in the output.
The reasons why it seems reasonable to do this:
- As George noticed, we would still keep the flags if the output
section had both an empty synthetic section and a regular section
- We need an heuristic to find the flags of output sections. Using the
flags of a synthetic section that would have been there seems a
reasonable heuristic.
llvm-svn: 326137
We sometimes need to iterate over input sections for a given
output section. It is not very convinent because we have to iterate
over section descriptions.
Patch introduces getInputSections helper, it simplifies things.
Differential revision: https://reviews.llvm.org/D43574
llvm-svn: 325763
Previously, in r320472, I moved the calculation of section offsets and sizes
for compressed debug sections into maybeCompress, which happens before
assignAddresses, so that the compression had the required information. However,
I failed to take account of relocations that patch such sections. This had two
effects:
1. A race condition existed when a debug section referred to a different debug
section (see PR35788).
2. References to symbols in non-debug sections would be patched incorrectly.
This is because the addresses of such symbols are not calculated until after
assignAddresses (this was a partial regression caused by r320472, but they
could still have been broken before, in the event that a custom layout was used
in a linker script).
assignAddresses does not need to know about the output section size of
non-allocatable sections, because they do not affect the value of Dot. This
means that there is no longer a reason not to support custom layout of
compressed debug sections, as far as I'm aware. These two points allow for
delaying when maybeCompress can be called, removing the need for the loop I
previously added to calculate the section size, and therefore the race
condition. Furthermore, by delaying, we fix the issues of relocations getting
incorrect symbol values, because they have now all been finalized.
llvm-svn: 321986
Moving the SHF_LINK_ORDER processing out of OutputSection::finalize()
means that we no longer need to copy all InputSections as we now only need
the first one.
Differential Revision: https://reviews.llvm.org/D40966
llvm-svn: 320478
By moving this step before thunk creation and other processing that depends
on the size of sections, we permit removal of duplicates in the .ARM.exidx
section.
Differential Revision: https://reviews.llvm.org/D40964
llvm-svn: 320477
The size of an OutputSection is calculated early, to aid handling of compressed
debug sections. However, subsequent to this point, unused synthetic sections are
removed. In the event that an OutputSection, from which such an InputSection is
removed, is still required (e.g. because it has a symbol assignment), and no longer
has any InputSections, dot assignments, or BYTE()-family directives, the size
member is never updated when processing the commands. If the removed InputSection
had a non-zero size (such as a .got.plt section), the section ends up with the
wrong size in the output.
The fix is to reset the OutputSection size prior to processing the linker script
commands relating to that OutputSection. This ensures that the size is correct even
in the above situation.
Additionally, to reduce the risk of developers misusing OutputSection Size and
InputSection OutSecOff, they are set to simply the number of InputSections in an
OutputSection, and the corresponding index respectively. We cannot completely
stop using them, due to SHF_LINK_ORDER sections requiring them.
Compressed debug sections also require the full size. This is now calculated in
maybeCompress for these kinds of sections.
Reviewers: ruiu, rafael
Differential Revision: https://reviews.llvm.org/D38361
llvm-svn: 320472
Fangrui Song